Source : Webster's Revised Unabridged Dictionary (1913)

Meniscus \Me*nis"cus\, n.; pl. L. {Menisci} (-s[=i]), E.
   {Meniscuses}. [NL., from Gr. ?, dim. of mh`nh the moon.]
   1. A crescent.

   2. (Opt.) A lens convex on one side and concave on the other.

   3. (Anat.) An interarticular synovial cartilage or membrane;
      esp., one of the intervertebral synovial disks in some
      parts of the vertebral column of birds.

   {Converging meniscus}, {Diverging meniscus}. See {Lens}.

Source : WordNet®

meniscus
     n : a disk of cartilage that serves as a cushion between the
         ends of bones that meet at a point
     [also: {menisci} (pl)]